Primary immune deficiencies (PIDs) are rare, life-threatening inherited defects in the immune system. The focus of the PID Treatment Consortium (PIDTC) will be on three PIDs that can be cured with hematopoietic cell transplantation (HCT), enzyme replacement or gene therapy: severe combined immunodeficiency (SCID), Wiskott-Aldrich syndrome (WAS) and chronic granulomatous disease (CGD). The objectives of the consortium are to characterize the long term outcomes and late effects in children with SCID, WAS and CGD who undergo HCT;to define the critical factors and biologic markers that influence the outcomes of children with SCID, WAS and CGD following HCT;to design and implement prospective clinical trials that improve care for children with PID;to prove the feasibility of newborn screening for SCID;and to provide training to physician scientists in the understanding and treatment of PIDs. Project 1 is a prospective study of SCID infants to identify early biomarkers and other disease- or HCT-related factors that affect engraftment, early immune reconstitution and survival. Project 2 is a cross-sectional retrospective study of SCID, exploring patient- and HCT-related factors that affect long term survival, immune reconstitution, late effects and quality of life. Project 3 addresses early and long-term outcomes following HCT in WAS and CGD, evaluating the degree of engraftment on outcome and identifying which patients with CGD are most likely to benefit from HCT. The Pilot Project Program will start with a Pilot Study of newborn screening for SCID. It will determine the efficacy of a novel test using newborn blood spots for early detection of SCID among Navajo Indians, who have a high incidence of SCID. The PIDTC encompasses 14 major centers that care for the majority of SCID, WAS and CGD patients in North America, bringing together for the first time physician/scientists with broad expertise in genetics, molecular biology, immunology, HCT, gene therapy and medical management. Parent advocacy groups will participate in PIDTC operations and oversight, subject recruitment, and dissemination of information resulting from our studies. These studies will resolve critical questions concerning HCT for these disorders and form the basis for future prospective clinical trials. RELEVANCE (See instructions): Primary immune deficiencies (PIDs) are rare, life-threatening inherited defects in the immune system. By forming this Consortium to compare different treatment approaches, improved survival and outcome should be afforded to future patients.